diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index d0094b6d..04af9cb8 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -60,6 +60,7 @@ module Sinatra
   # http://rack.rubyforge.org/doc/classes/Rack/Response/Helpers.html
   class Response < Rack::Response
     def body=(value)
+      value = value.body while value.respond_to? :body and value.body != value
       @body = value.respond_to?(:to_str) ? [value.to_str] : value
     end
 
diff --git a/test/response_test.rb b/test/response_test.rb
index 826defdc..6c70b60a 100644
--- a/test/response_test.rb
+++ b/test/response_test.rb
@@ -39,4 +39,14 @@ class ResponseTest < Test::Unit::TestCase
     assert_equal '14', headers['Content-Length']
     assert_equal @response.body, body.body
   end
+
+  it 'does not nest a Sinatra::Response' do
+    @response.body = Sinatra::Response.new ["foo"]
+    assert_equal @response.body, ["foo"]
+  end
+
+  it 'does not nest a Rack::Response' do
+    @response.body = Rack::Response.new ["foo"]
+    assert_equal @response.body, ["foo"]
+  end
 end